Process for the preparation of {60 -ketocarboxylic acids

ABSTRACT

A process for the preparation of Alpha -keto-carboxylic acids for the formula: R-CO-COOH in which R represents an aliphatic, aromatic, aralkyl, alicyclic or heterocyclic radical which may or may not be substituted which comprises treating a Alpha -hydroxy carboxamide of the formula:   WHEREIN A represents a hydrogen atom or an aliphatic or aralkyl radical, A&#39;&#39; and A&#39;&#39;&#39;&#39; each represent an aliphatic or aralkyl radical or form, together with the carbon atom to which they are bonded, a cycloalkane residue and R represents an aliphatic, aromatic, aralkylic, alicyclic or heterocyclic radical which may or may not be substituted with an oxidizing agent, and hydrolysing in acid medium the Alpha -ketocarboxamide so obtained of the formula:   WHEREIN A, A&#39;&#39;, A&#39;&#39;&#39;&#39; and R have the same meaning as above; Alpha -ketocarboxamides of the formula:   WHEREIN R, A, A&#39;&#39; and A&#39;&#39;&#39;&#39; have the meanings given above and 3,3dibenzylpyruvic acid.

[451 July 29, 1975 United States Patent Anatol i 1 PROCESS FOR THE PREPARATION OF a-KETOCARBOXYLIC ACIDS Jesus Anatol, Paris, France [75] Inventor:

\[73] Sucreries du Soissonnais et Compagnie Scuriere, Paris, France Filed: Mar. 2, 1972 Appl. No.: 231,381

Assignee:

Foreign Application Priority Data Mar. 2, 1971 France 71.07097 US. Cl 260/406; 260/515 R; 260/526 R; 260/558 R; 260/561 K; 260/562 K; 260/4l3 Int. CL CO7D 59/33; CO7D 59/34; CO7D 65/20 Field of Search 260/515 R, 483, 526 R, 260/406 References Cited UNITED STATES PATENTS 8/1948 Price et al 260/406 Primary ExaminerAnton H. Sutto Assistant ExaminerMichael Shippen [57] ABSTRACT A process for the preparation of a-keto-carboxylic acids for the formula: R-CO-COOH in which R represents an aliphatic, aromatic, aralkyl, alicyclic or heterocyclic radical which may or may not be substituted which comprises treating a a-hydroxy carboxamide of the formula:

wherein A represents a hydrogen atom or an aliphatic or aralkyl radical, A and A" each represent an aliphatic or aralkyl radical or form, together with the carbon atom to which they are bonded, a cycloalkane residue and R represents an aliphatic, aromatic, aralkylic, alicyclic or heterocyclic radical which may or may not be substituted with an oxidizing agent, and hydrolysing in acid medium the a-ketocarboxamide so obtained of the formula:

wherein A, A, A" and R have the same meaning as above; a-ketocarboxamides of the formula:

wherein R, A, A and A" have the meanings given above and 3,3-dibenzylpyruvic acid.

13 Claims, N0 Drawings PROCESSFOR PREPARATION OF a-KETOCARBOXYLICACIDS The invention relates to a new general process for the preparation of aketocarboxylic acids of general formula: RC O-CO OH. 1

Among these acids a good many are essential intermediates of metabolism either as precursors of a-amino acids or intervening in the processes of transmamination or taking part in gluc idic metabolism. H

These acids may also be used as intermediate prodnets in the manufacture of dyestuffs' Their synthesis has formed the subject of a number of important works which can be summarised as follows: v j

1. Action of an acid halide upon a metal cyanide (copper or silver) followed by hydrolysis; V

R-CO Hal -l- Met.CN R-CO-CN R-CO-COOH This method fails to give appreciable results when R in an aliphatic series contains more than 3 carbon atoms (L. GLAISEN and F. MORITZ Ber. 13-1880 p. 2121; W. TSCHELINZEFF and W. SCHMIDT Ber. 62-1929 p. 2210).

2. Hydrolysis of the esters of 2-hydroxyimino carboxylic acids according to the method of R. BOU- VEAULT and L. LOCQUIN (C. R. Acad. Sci. 135, 1902 p. 179).

a-cn-coo-c H 4 2 004313 OH so no R4; cooc u a-co-coou NOH F. ADICKES and G. ANDRESSEN vAnn. 555, 1944/41 observe that the yields are low and adopt the following process 3.

3. Condensation of esters of aliphatic carboxylic acids with ethyl oxalate in the presence of sodium ethoxide. (W. WISLICENUS, Ber. 20, 1887 p. 589 p. 3392 and p. 3394):

5. Action of an excess of piperidine upon the esters of aliphatic a,,B-c1ibrominated carboxylic acids and acid hydrolysis of the esters of the 0:,B-dipiperidino-carboxylic acid so obtained. (H. MOUREAUX and others Bul. Soc. Chim. 1952 p. 296 and 442).

However, the authors mention that their process is of limited applicability; thus for example dimethyl acrylic acid does not lead to 2-oxo-isovaleric acid.

6. Hydrogenation by potassium hydroboride of 4-phenyl-2-oxo-3-butene carboxylic acids and treatment with sodium hydroxide at elevated temperature of the 4-pheny1-2-hydroxy-3-butene carboxylic acids, by which treatment the corresponding saturated a-keto acids are obtained. (P. COR- DlER Bul. soc. chim. 1956 p. 564).

7. Conversion of the 2-trif1uoroacetylamino carboxylic acids to 2-trifluoromethyl-5-oxazolones followed by isomerisation and by hydrolysis to a-keto acids (F. WEYGAND et al. Ann. 658, 1962 p. 128).

8. Synthesis of a-ketocarboxylic acids starting from esters of alkylidenecyano acetic acids (M.l. GARASHI and H. MIDORIKAWA (J. Orgn. Chem. 28, 1963 p. 3088 and 32, 1967 p. 3399).

9. Action of organo-lithium derivatives upon isonitriles followed bycarbonation of the aldimine lithium so obtained and hydrolysis (H. M. WAL- BORSKY and G. E. NIZNIK J. Am. Chem. Soc. 91 1969 p. 7778).

10. Oxidation of a-hydroxy acids (G. V. BAKORE J. Chem. Soc. 1963 p. 3419) or their esters (T. KUWATA'J. Am. Chem. Soc. 1938 p. 559). The tests carried out in this direction were not conclusive.

It has now been found that it is possible to obtain, a-ketocarboxylic acids, in general in very good yields, by a process which comprises treating a a-hydroxy carboxamide of the general formula:

R CHOH GONH C wherein A represents a hydrogen atom or an aliphatic or aralkyl radical, A and A" each represent an aliphatic or aralkyl radical or form, together with the carbon'atom to which they are linked, a cycloalkane residue, and R represents an aliphatic, aromatic, aralkyl, alicyclic or heterocyclic residue which may or may not be substituted with an oxidizing agent and in hydrolyzing in acid medium the a-ketocarboxamide so obtained of formula:

wherein A, A, A" and R have the meanings given above.

The ketocarboxamides of formula 11 are new products;

they form as such part of the invention. Among them may be mentioned in particular the N-tert.butyl a-ketocarboxamides, the hydrocarbonradical R of which possesses 1 to 15 carbon atoms. These compounds of formula 11 are perfectly stable and lend themselves well to purificationjeither by distillation or by recrystallization from solvents. v I A The a-hydrox'y carboxamides which may be used'as starting materials for the carrying out of the process of the invention can be obtained for example according to known processes, by condensation in acid medium of secondary or tertiary alcohols of the general formula:

wherein A, A and A" have the meanings given above with 2-hydroxy nitriles of formula RCHOHCN. The oxidizing treatment of the a-hydroxy carboxamides of formula 1 can be effected for example withmineral oxidants such as: permanganates, manganese dioxide or chromium trioxide. The latter is particularly advantageous, since the salts resulting from its reduction do not give rise to precipitates; I

The hydrolysis of the a-ketocarboxamides by acids may be effected for example either inaqueous medium, or in a solvent, at a temperature up to boiling point. The medium may advantageously consist of acetic acid.

The a-ketocarboxylic acids can be separated simply for example by dilution of the reaction medium from which they crystallize or by extraction with organic solvents, if their solubility in water is appreciable. They can be purified for example by distillation or by recrystallization. Some of them, moreover, are new products.

The invention is illustrated by the following Examples in which the parts specified are parts by weight unless otherwise stated. 7

EXAMPLE 1 Preparation of 2-oxo-isovaleric acid A. 49.5 parts of 3,3-dimethy1-2-hydroxypropanenitrile prepared according to a classical method from isobutyraldehyde are dissolved in 75 parts by volume of tert-butyl alcohol. To this solution are added 75 parts by volume of 66Be sulphuric acid with cooling so that the internal temperature should not exceed 50C. The mixture is allowed to stand overnight, then the reaction mass is diluted with 400 parts of water and the'suspension so obtained is neutralized by the addition of a concentrated solution of sodium hydroxide.

Analysis for Calculated:

Found:

B. 43 parts of the 2-hydroxy isovaleramide obtained above are dissolved in parts by volume of acetic acid. Furthermore, 21 parts of chromium trioxide (CrO are dissolved in 20 parts of water with parts by volume of acetic acid. The second solution is poured into the first; a moderate rise in temperature occurs. The mixture is allowed to stand overnight, then it is diluted with 300 parts of water and extracted with ether (3 times 100 parts by volume). The ether layer is washed witha 4 N sodium hydroxide solution and then with water. The ether is removed at'reduced pressure and the residue is distilled (B.p. 81C/ 10 mm). 7

34 parts of 2-oxo-N-tert.butyl isovaleramide are obtained, that is a yield of distilled product of 73%.

Analysis for C H NO M.W. 171

Calculated: C% 63.12 H% 10.01 N% 8.18 Found: 63.13 10.00 8.15

This compound gives as a characteristic derivative the 2',4-dinitro-2-phenylhydrazono-N.tert-butyl isovaleramide. M.p. 151C.

Analysis for C H N Q, M.W. 351

Calculated: C% 51.28 H% 6.02 N% 19.93 Found: 51.31 6.17 19.95

Analysis for C l-1 0;, M.W. 116 Calculated: C% 51.72 H% 6.94 Found: 51.55 7.04

Characteristic derivative:

2 ',4-dinitro-2-pheny1hydrazonoisovaleric acid.

Analysis for l 1 c u mo, M.W. 296

Calculated: c% 44.60 11% 4.08 14% 18.91 Found: 44.59 4.04 18.88

. E A PLE; T v V I Preparation of 3,3-dibenzyl pyruvic acid This a-ketoacid has not been described in the literature.

A. lnto a 3-necked flask fitted with a stirrer and a 5 thermometer, are placed 92 parts of monopotassium phosphate, 200 parts of water and 150 parts of dibenzyl acetaldehyde.

The stirrer is started and 53 parts of commercial potassium cyanide dissolved in 200 parts of water are added all at once; the temperature rises to 4l-42C. Stirring is continued for 2 to 3 hours.

The medium containing the 3,3-dibenzyl-2- hydroxypropanenitrile which is formed (J. ANATOL C. R. Acad. Sci. 235, 1952 p. 249) is taken up in ether (450 75 75). The ether solution is washed with 2 N sulphuric acid (2X25) then with water (2X25). It is dried over anhydrous sodium sulphate, filtered and the ether is removed at reduced pressure. The residue so-. lidifies. Its weight is that indicated by theory. To recrystallize the product it is dissolved in 175 parts by volume of benzene at elevated temperature, 350 parts of petroleum ether are added, the product is filtered and dried. 153 parts of recrystallized product are obtained. M.p. 97C. Yield 91%.

Analysis for c,,H,,No M.w.=251.3 Calculated: c%s1.24 14% 6.82 N% 5.57 Found: 81.20 6.94 5.64

75 parts of 3,3-dibenzyl-2-hydroxy-propanenitrile are dissolved in 300 parts by volume of trimethyl carbinol. To this solution, without exceeding 50C. and with stirring, are added parts by volume of 66Be sulphuric acid. The mixture is allowed to stand for 48 hours, it is heated to 75C. for one hour, 450 parts of cold water are added and the emulsion is neutralized in the presence of phenolphthalein with a solution of sodium hydroxide. An oil separates on top which soon solidifies. It is filtered, washed and dried. 95 parts of 3,3 dibenzyl N.tert-buty1 lactamide are obtained, that is a yield of 97.9%.

By recrystallization from ethyl acetate beautiful needles are obtained. M.p. 166C.

. Analysis for CHHNNOZ M.W. 325 Calculated: C% 77.54 H% 8.31 N% 4.31

Found: 77.32 8.20 4.32

B. 47 parts of the above lactamide are dissolved in 188 parts by volume of acetic acid. Furthermore, I 1.7 parts of chromium trioxide are dissolvedin 48 parts of acetic acid. The two solutions are mixed, the mixture is heated to 90-95C. for 4 hours and 250 parts of water are added. l i

'To remove the tracesof chromium salt, the mixture is extracted with ether (150 50), the-ether layers are washed with 'a' solution of 5 N sodium hydroxide (2X25) until'alkaline and the n'with'watenglhe ether solutions are dried and the ether'isremoved:=45 .8-parts 65 of an oil are obtained which crystallizes. The crystals are dissolved at elevated temperature in parts by volume of hexane, allowed to crystallize, filtered and dried. 41 parts of 3,3-dibenzyl N.tert-butyl pyruvamide are obtained, that is a yield of 90% in recrystallized Characteristic derivative: 2',4'-dinitro-2-phenylhydrazono-3,'3-dibenzy1 N.tert-butyl-propanamide Cg7H29N5O5M.p.

C. 19.3 parts of 3,3-dibenzyl N.tert-butyl pyruvamide are dissolved in parts by volume of acetic acid and 145 parts of hydrochloric acid (d=l.l9). The solution is heated under reflux during 24 hours, 500 parts of water are added and the crystallization is initiated. The crystallized product is filtered and washed with water.

Under such conditions, the a-keto acid retains very large quantities of water. It is dissolved at elevated temperature in 65 parts by volume of benzene, the solution is filtered and the benzene is eliminated. 15.6 parts (theory 15.8) of an oil remain which commences to crystallize. It is dissolved in 65 parts of cyclohexane at elevated temperature, allowed to crystallize, the crystals are filtered, washed and dried until of constant weight. 13.8 parts of 3,3-dibenzyl pyruvic acid are obtained, that is a yield of 87.3% of recrystallized product. M.p. 77C. This acid crystallizes in large prisms, forming twin crystals.

Analysis for CHHWOQ M.W. 268 M.p. 77C.

Calculated: C% 76.11 H% 5.97 Found: 75.99 6.02

Characteristic derivative: 2',4-dinitro-2-phenylhydrazono-3,3-dibenzyl propionic acid. M.p. 189C.

The following Table I gives the characteristics of dif-- ferent hydroxy-amides of formula:

The following Table 11 givesthe characteristics of new oxo-amides of formula:

I CH R-Cl-lOl-l-CN in which R has the above meanings to form the corresponding a-hydroxy carboxamide of the R CO CO NH C CH formula v obtained according to processes B of the preceding Exj 4 g amples. 1\.!l1O. l-CUN'n-l'- A In the column Analyses c and fmean calculated A H and found respectively. The column RNHN= gives the melting point of the 2',4'-dinitro-2- 3 phenylhydrazono derivative of the ketoamide. wherein R, A, A and A have the above meanings,

TABLE II R M.W. M.p. 0r Yields Analyses RNHN= B.p. C71 H71 Nvt ethyl 157 34C. 5671 e 61.12 9.62 8.91 164C.

82/l4 nlm f 6105 9.59 8.80 propyl 171 90/10 mm 61% c 63.12 10.01 8.18 159C.

1 63.26 10.01 8.26 ht-n l 205 77C. 82% C 70.22 7.37 6.82 252C.

f7().21 7.30 6.90 ht-hz l 19 53C. 78% C 71.21 7.80 6.39 201Cv l" 71.04 7.92 6.33 fi'phtnyh 233 47C. 87% c 72.07 8.21 6.00 152C.

ethyl f72.82 8.16 5.93 diphenyl- 295 103C. 60% c 77.26 7.17 4.74 165C.

methyl 1' 77.22 7.21 4.78

hexyl 2 l 3 98C/ I mnl 70% 130C. nonyl 255 96C/().5 X171 87C.

The following Table III gives the characteristics of b. oxidizing said a-hydroxy carboxamide with an oxidifferent acids of formula RCOCOOH prepared dizing agent in solution to form an a-ketocarboxaaccording to processes C of the preceding Examples. mide of the formula:

TABLE III R M.W. M.p. or B.p. Yields Analyses RNHN= ethyl 102 66-67C. 48% c 47.06 5.92 180C.

12 mm f46.72 5.84 pmpyl 1 16 78-79C. 55% C 51.72 6.94 109C.

12 mnl f 51.86 7.09 phenyl 150 62C. 82% c 64.00 4.03 193C.

f 6405 3.99 hcnlfl 164 150C. 6071 c 65.85 4.91 183C.

f 65.65 4.96 fi-phellyl- 17X 44C. hl /z e (1740 5.00 IC ethyl r6732 5.7-1 tll hhn l- 240 113C. 88% C 74.98 5.03 210C.

methyl f 75.02 5.03

ht-x l 158 62C./0.5 72% 131C.

0.32 nlnl llonyl 00 45C. 79% 125C.

1 claim: A

l. A process for the preparation of an a-ketocarboxyh-eo-comz A I lic acid of the formula: RCOCOOH, in which R is selected from the group consisting of aliphatic, benzyl, phenyl and aralkyl radicals, which consists essentially of the successive steps of a. condensing in acid medium a secondary or tertiary alcohol of the formula 55 wherein A, A, A" and R have the same meanings as above and further wherein said oxidizing agent is selected from the group consisting of chromium trioxide, manganese dioxide and permanganates; and

c. hydrolyzing said a-ketocarboxamide in an acid medium to form said a-ketocarboxylic acid.

2. The process as defined in claim 1 wherein A, A and A are methyl.

3. The process as defined in claim 2 wherein said oxidizing agent is an aqueous solution of chromium trioxide and ace.tic'acid.-

4. A process for. the preparation of a-ketocarboxylic acids of the formula RCOCOOH, in which R is sewherein R has the above meaning and A represents a methyl radical,

b. oxidizing said a-hydroxy carboxamide with CrO in an aqueous acetic acid solution, c. hydrolyzing the so formed a-keto carboxamide in acid medium, and

10 d. separating and collecting the a-ketocarboxylic acid which is formed.

5. A process according to claim 4 wherein R is an ethyl radical.

6. A process according to claim 4 wherein R is a propyl radical.

7. A process according to claim 4 wherein R is a phenyl radical.

8. A process according to claim 4 wherein R is a benzyl radical.

9. A process according to claim 4 wherein R is a betaphenyl ethyl radical.

10. A process according to claim 4 wherein R is a diphenyl methyl radical.

11. A process according to claim 4 wherein R is an hexyl radical.

12. A process according to claim 4 wherein R is a nonyl radical.

13. A process according to claim 4 wherein R is a dibenzyl methyl radical.

UNITED STATES PATENT AND TRADEMARK OFFICE QEERTIFICATE OF CORRECTION PATENT NO. S,897,l1.67 DATED 1 y 9, 975 |N\/ ENTOR(S) Jesus Anatol It rs certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The name of the assignee must read:

SUCRERIES DU SOISSONNAIS ET COMPAGNIE SUCRIERE Signed and Scaled this Thirteenth Day of July 1976 {SEAL} A ttes t:

RUTH C. MASON Commissioner 91' Parents and Trademark: 

1. A PROCESS FOR THE PREPARATION OF AN A-KETOCARBOXYLIC ACID OF THE FORMULA: R-CO-COOH, IN WHICH R IS SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC, BENZYL, PHENYL AND ARALKYL RADICALS, WHICH CONSITS ESSENTIALLY OF THE SUCCESSIVE STEPS OF A. CONDENSING IN ACID MEDIUM A SECONDARY OR TERTIARY ALCOHOL OF THE FORMULA
 2. The process as defined in claim 1 wherein A, A'' and A'''' are methyl.
 3. The process as defined in claim 2 wherein said oxidizing agent is an aqueous solution of chromium trioxide and acetic acid.
 4. A process for the preparation of Alpha -ketocarboxylic acids of the formula R-CO-COOH, in which R is selected from the group consisting of aliphatic, benzyl, phenyl and aralkyl radicals, which consists essentially of the successive steps of a. condensing, in sulphuric acid medium, tertbutyl alcohol with a 2-hydroxy nitrile of the formula R-CHOH-CN in which R has the above meaning, to form the corresponding Alpha -hydroxy-N-tert-butyl carboxamide of the formula
 5. A process according to claim 4 wherein R is an ethyl radical.
 6. A process according to claim 4 wherein R is a propyl radical.
 7. A process according to claim 4 wherein R is a phenyl radical.
 8. A process according to claim 4 wherein R is a benzyl radical.
 9. A process according to claim 4 wherein R is a beta-phenyl ethyl radical.
 10. A process according to claim 4 wherein R is a diphenyl methyl radical.
 11. A process according to claim 4 wherein R is an hexyl radical.
 12. A process according to claim 4 wherein R is a nonyl radical.
 13. A process according to claim 4 wherein R is a dibenzyl methyl radical. 